Fitch Rates Wells Fargo P-T Ctfs $200.06MM Series 2006-20.

NEW YORK -- Wells Fargo mortgage pass-through certificates, series 2006-20, are rated by Fitch Ratings as follows:

-- $196,555,047 classes A-1, A-PO, and A-R 'AAA' (senior certificates);

-- $2,303,000 class B-1 'AA';

-- $400,000 class B-2 'A';

-- $401,000 class B-3 'BBB';

-- $200,000 class B-4 'BB'; and

-- $200,000 class B-5 'B'.

The 'AAA' ratings on the senior certificates reflect the 1.85% subordination provided by the 1.15% class B-1, the 0.20% class B-2, the 0.20% class B-3, the 0.10% privately offered class B-4, the 0.10% privately offered class B-5, and the 0.10% privately offered class B-6. The ratings on the class B-1, B-2, B-3, B-4, and B-5 certificates are based on their respective subordination. Class B-6 is not rated by Fitch.

Fitch believes the amount of credit enhancement available will be sufficient to cover credit losses. The ratings also reflect the high quality of the underlying collateral, the integrity of the legal and financial structures, and the primary servicing capabilities of Wells Fargo Bank, N.A. ([WFB]; rated 'RPS1' by Fitch).

The transaction consists of one group of 319 fully amortizing, fixed interest rate, first lien mortgage loans, with an original weighted average term to maturity (WAM) of approximately 15 years. The aggregate unpaid principal balance of the pool is $200,260,197 as of Nov. 1, 2006 (the cut-off date), and the average principal balance is $627,775. The weighted average original loan-to-value ratio (OLTV) of the loan pool is approximately 62.73%. The weighted average coupon (WAC) of the mortgage loans is 6.190%, and the weighted average FICO score is 751. The states that represent the largest geographic concentration are California (23.89%), Texas (7.53%), New York (7.12%), and New Jersey (6.46%). All other states represent less than 5% of the outstanding balance of the pool.

None of the mortgage loans are 'high cost' loans as defined under any local, state, or federal laws. For additional information on Fitch's rating criteria regarding predatory lending legislation, see the press release 'Fitch Revises Rating Criteria in Wake of Predatory Lending Legislation,' dated May 1, 2003, available on the Fitch Ratings web site at www.fitchratings.com.

All of the mortgage loans were generally originated in conformity with underwriting standards of WFB. WFB sold the loans to Wells Fargo Asset Securities Corporation (WFASC), a special purpose corporation, who deposited the loans into the trust. The trust issued the certificates in exchange for the mortgage loans. WFB will act as servicer and custodian, and HSBC Bank USA, National Association will act as trustee. Elections will be made to treat the trust as one real estate mortgage investment conduit (REMIC) for federal income tax purposes.

Fitch's rating definitions and the terms of use of such ratings are available on the agency's public site, www.fitchratings.com. Published ratings, criteria and methodologies are available from this site, at all times. Fitch's code of conduct, confidentiality, conflicts of interest, affiliate firewall, compliance and other relevant policies and procedures are also available from the 'Code of Conduct' section of this site.